Apparatus for Apertured Attachment of Metal Sheets

ABSTRACT

Apparatus attaches together stacked upper and lower metal sheets and provides a reinforced aperture. A lower die has a die groove and an opening in the center of the die groove. An upper die has an annular end face that registers with the die groove and a spring-loaded reciprocable punch button that registers with the opening. A hollow ring-shaped grommet has an annular upper end flange engaged by the annular end face of the upper die and an axially extending tubular wall longer than the stacked thickness of the sheets. A metal piercing point at the terminal end of the axially extending wall pierces through the stacked upper and lower sheets and into engagement with the die groove of the lower die to progressively bend the axially extending wall radially outward and upward into engagement with the lower sheet, thereby attaching the sheet together and providing a reinforced aperture.

FIELD OF THE INVENTION

The present invention relates to apparatus for attaching together stacked upper and lower metal sheets, and more particularly an attachment of metal sheets that simultaneously provides an aperture through the sheets.

BACKGROUND OF THE INVENTION

It is well known in automotive and other manufacturing industries that two sheets of metal can be attached together by laying one sheet atop the other and then installing a fastener therebetween.

It is also known in the manufacturing industries to provide an aperture through a metal sheet, or through a stack of metal sheets, for various purposes such as providing an aperture for the drainage of water, or providing an aperture for receiving a locating pin to precisely locate the metal during the conduct of manufacturing processes such as stamping, or for precisely locating the sheet for measuring and gauging operations. It would be desirable to provide a new and improved apparatus by which metal sheets could be attached together, but at the same time a reinforced aperture could be provided through the sheets.

SUMMARY OF THE INVENTION

Apparatus is provided for attaching together stacked upper and lower metal sheets, while at the same time providing a reinforced aperture through the attached together sheets. A lower die is provided having a die groove that underlies the lower sheet and an opening in the center of the die groove. An upper die has an annular end face that overlies and registers with the die groove of the lower die. A spring-loaded punch button is reciprocable within the upper die and registers with the opening in the lower die. A ring-shaped grommet has an annular upper end flange for engagement by the annular end face of the upper die and an axially extending tubular wall of greater length than the stacked thickness of the upper and lower metal sheets. The axial extending wall of the grommet has a metal piercing point at the terminal end thereof so that upon lowering of the upper die, the annular end face of the upper die forces the metal piercing point to pierce through the stacked upper and lower sheets and into engagement with the die groove of the lower die to progressively bend the axially extending wall radially outward and upward into engagement with the lower sheet. Thus the sheets are attached together by being captured between the annular upper end flange and the outward bent axially extending tubular wall. The hollow ring shape of the grommet provides an aperture through the attached together sheets and reinforces the aperture made through the metal sheets.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1 is a section view taken through the apparatus of this invention and showing the press in an open position with the upper die poised above the lower die;

FIG. 2 is a perspective view of the grommet of this invention having parts broken away and in section;

FIG. 3 is a view similar to FIG. 1 but showing the upper die partly lowered onto the lower die so that the grommet is pressed against the upper metal sheet;

FIG. 4 is a view similar to FIGS. 1 and 3 but showing the upper die lowered further so that the grommet is piercing through the stacked metal sheets;

FIG. 5 shows the upper die fully lowered to have installed the grommet and so that the spring-loaded die button of the upper die has bent the pierced metal discs for disposal through the opening of the lower die; and

FIG. 6 is a view similar to FIG. 2 but showing the grommet installed to attach the sheets and provide a reinforced aperture through the stacked sheets.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The following description of certain exemplary embodiments is exemplary in nature and is not intended to limit the invention, its application, or uses.

Referring to FIG. 1, a press includes a fixed lower platen 12 and a vertically movable upper platen 14.

A pair of metal sheets, particularly an upper metal sheet 18 and a lower metal sheet 20 are stacked and laid upon the lower platen 12. A lower die 24 is mounted on the lower platen 12. The lower die 24 is annular in shape and has a central opening 26 there through that is defined by a stepped bore 28 including an upper bore portion 30 and a lower chute portion 32 that is larger in diameter than the upper bore portion 30. The upper end face of the lower die 24 has a circumferential extending die groove 36 that cooperates with the stepped bore 28 to provide an annular circumferential extending knife edge 38. The tip of knife edge 38 has a bevel 40 that slants in a radially outward direction. The die groove 36 is substantially U-shaped in cross section and extends continuously around the circumference of the lower die 24.

FIG. 1 also shows an annular upper die 46 that is mounted on the press upper platen 14. Upper die 46 has a central bore 48 that overlies and registers with the upper bore portion 30 of the lower die 24. A cylindrical punch button 50 is reciprocably mounted in the central bore 48 of the upper die 46 and is supported by a coil compression spring 54 that seats between the punch button 50 and the upper platen 14. FIG. 1 shows the coil compression spring 54 at its free uncompressed length and it is seen that the punch button 50 is thereby poised above the upper bore portion 30 of the lower die 24. The upper die 46 has an annular end face 58 that generally overlies the die groove 36 of the lower die 24, and the punch button 50 extends downwardly beyond the annular end face 58 as shown in FIG. 1.

In FIG. 1, it is seen that a ring-shaped grommet 62 is positioned on the upper die 46 with the punch button 50 extending through the ring-shaped grommet 62.

Referring to FIG. 2, it is seen that the ring-shaped grommet 62 is a hollow circular shape and includes at its upper end an annular upper end flange 64. The ring-shaped grommet 62 also includes a tubular axially extending wall 66 that depends downwardly from the upper annular end flange 64 and is integral therewith. The terminal end of the axially extending wall 66 has a circumferential extending metal piercing point 72 that is beveled outwardly at 74.

Referring again to FIG. 1, it will be understood that the grommet 62 has been loaded onto the upper die 46 and is held in place thereon, for example by friction or by magnetic attraction. The length of the axially extending wall 66 is several times the combined thickness of the stacked metal sheets 18 and 20, for reasons that will be discussed hereinafter. Punch button 50 has a dome shaped lower end face 80, including a generally flat center portion 82 and a tapered radially outer portion 84.

Referring to FIG. 3, it is seen that the upper platen 14 has been lowered so that the grommet 62 has been lowered into contact with the upper sheet 18 and the lower end face 80 of the punch button 50 has also been lowered into contact with the upper sheet 18 and the spring 54 is partly depressed. Accordingly, as seen in FIG. 3, the metal piercing point 72 of the grommet 62 is precisely aligned with the knife edge 38 of the lower die 24, so that a further lowering of the upper platen 14 will cause the upper sheet 18 and lower sheet 20 to be sheared between the metal piercing point 72 and the knife edge 40.

Referring to FIG. 4, it is seen that the upper platen 14 has been lowered further from its position of FIG. 3 so that the upper die 46 has forced the grommet 62 to pierce through the upper sheet 18 and lower sheet 20, thereby creating a severed disc 90 of the upper sheet 18 and a severed disc 92 of the lower sheet 20 as shown in FIG. 5. Also, the domed lower end face 80 of the punch button 50 has caused the bending of severed discs 90 and 92 into a dome shape, thereby reducing the diameter of the severed discs 90 and 92, to facilitate passage through the upper bore portion 30 of the stepped bore 28.

Referring to FIG. 5, it is seen that the upper platen 14 has been fully lowered, causing the axially extending wall 66 of the grommet 62 to have come into contact with the die groove 36 of the lower die 24 so that the axially extending wall 66 has been deflected and bent radially outward and then upwardly into engagement with the underside of the lower sheet 20. As a result, the sheets 18 and 20 have become captured between the annular upper end flange 64 of the grommet 62 and the outwardly and upwardly bent axially extending wall portion 66 of the grommet 62. Simultaneously, the final downward stroke of the upper platen 14 and the extension of the coil compression spring 54 has caused the punch button 50 to have pushed the discs 90 and 92 through the lower chute portion 32 of the stepped bore 28 for disposal out the bottom of the lower platen 12.

After the upper die 46 has been fully lowered and the grommet 62 installed, the upper die 46 will be reversed and lifted back to its open position of FIG. 1. Thereafter, the sheets 18 and 20 can be removed from the press.

Referring to FIG. 6, the finished product is shown and it is seen that the upper sheet 18 and lower sheet 20 have been effectively attached together by the installation of the grommet 62. In addition, it is seen that the hollow interior of the ring shape of the grommet 62 has simultaneously provided a reinforced aperture 96 through the attached together sheets 18 and 20. For example, the aperture 96 can provide a drainage hole if the assembled sheets are exposed to weather conditions. Alternatively, the aperture through the attached sheets facilitates the positioning of the attached together sheets over a locating pin, such as commonly employed in precisely locating panels during manufacturing operations or precisely locating the panels for measuring and gauging operations.

Thus, it is seen that the invention provides a new and improved apparatus for joining together two or more metal sheets, while simultaneously forming a reinforced aperture through the attached together sheets.

The description of the invention is merely exemplary in nature and, thus, variations thereof are intended to be within the scope of the invention. Although the drawings herein show the example of two stacked sheets, it will be understood that three or more sheets may be stacked and attached together. The hollow ring shape of the grommet is not limited to being circular, but can be oval, rectangular, or other shape, including the shape of the trademark of the manufacturer. 

1. Apparatus for attaching stacked upper and lower metal sheets comprising: a lower die having a die groove that underlies the lower sheet and an opening in the center of the die groove; an upper die having an annular end face that overlies the upper sheet and registers with the die groove of the lower die; a spring-loaded punch button that is reciprocable within the upper die and registers with the opening in the lower die; and a ring-shaped grommet having an annular upper end flange for engagement by the annular end face of the upper die and an axial extending wall of greater length than the stacked thickness of the upper and lower metal sheets, said axial extending wall having a metal piercing point at the terminal end thereof so that upon lowering of the upper die the annular end face forces the metal piercing point to pierce through the stacked upper and lower sheets and into engagement with the die groove of the lower die to bend the axial extending wall radially outward and upward to engage with the lower sheet whereby the sheets are attached together by capture between the annular upper end flange and the outward bent axial extending wall and the hollow ring shape of the grommet provides an aperture through the attached together sheets.
 2. The apparatus of claim 1 further comprising said spring-loaded punch having a dome shaped end face that engages the top sheet and bends the severed portions of the upper and lower sheets for disposal through the opening in the center of the lower die surface.
 3. The apparatus of claim 1 further comprising said lower die having a circumferential knife edge that registers with the metal piecing point of the grommet to aid in severing the discs.
 4. The apparatus of claim 3 further comprising said circumferential knife edge having a bevel that deflects the axial extending wall of the grommet radially outward upon the severing of the metal discs.
 5. The apparatus of claim 1 further comprising said opening of the lower die being a stepped bore having an upper portion that is of a diameter to receive the punch and a lower chute portion that is of a diameter greater than the diameter of the punch face to facilitate the disposal of the severed discs.
 6. The apparatus of claim 5 further comprising said spring-loaded punch having a dome shaped end face that engages the top sheet and bends the severed portions of the upper and lower sheets for disposal through the opening in the center of the lower die surface.
 7. Apparatus for attaching stacked upper and lower metal sheets comprising: a lower die having a die groove that underlies the lower sheet and an opening in the center of the die groove, said opening being a stepped bore including an upper bore portion and a lower chute portion of greater diameter than the upper bore portion; an upper die having an annular end face that overlies the upper sheet and registers with the die groove of the lower die and a central bore that overlies the opening of the lower die; a punch reciprocable within the central bore of the upper die; a coil compression spring urging the punch to an extended position extending beyond the annular end face of the upper die; a grommet seated on the punch and having an annular upper end flange driving the annular end face of the upper die and an axial extending wall of greater length than the stacked thickness of the upper and lower metal sheets, said axial extending wall having a metal piercing point at the terminal end thereof so that upon lowering of the upper die the annular end face forces the metal piercing point to pierce through the stacked upper and lower sheets and into engagement with the die groove of the lower die to bend the axial extending wall radially outward and upward to engage with the lower sheet whereby the sheets are attached together by capture between the annular upper end flange and the outward bent axial extending wall.
 8. The apparatus of claim 7 further comprising said opening of the lower die being a stepped bore having an upper portion that is of a diameter to receive the punch and a lower chute portion that is of a diameter greater than the diameter of the punch face to facilitate the disposal of the severed discs.
 9. The apparatus of claim 8 further comprising said spring-loaded punch having a dome shaped end face that engages the top sheet and bends the severed portions of the upper and lower sheets for disposal through the opening in the center of the lower die surface.
 10. The apparatus of claim 7 further comprising said lower die having a circumferential knife edge that registers with the metal piecing point of the grommet to aid in severing the discs.
 11. The apparatus of claim 10 further comprising said circumferential knife edge having a bevel that deflects the axial extending wall of the grommet radially outward upon the severing of the metal discs.
 12. The apparatus of claim 7 further comprising said grommet being a hollow ring shape so that upon installation of the grommet to attach together the stacked sheets, a reinforced aperture is simultaneously provided through the sheets.
 13. The apparatus of claim 7 further comprising said spring-loaded punch having a dome shaped end face that engages the top sheet and bends the severed portions of the upper and lower sheets for disposal through the opening in the center of the lower die surface.
 14. Apparatus for attaching stacked upper and lower metal sheets comprising: a lower die having a circumferential extending knife edge extending upwardly, a circumferential die groove located radially outward from and surrounding the knife edge, and an opening located radially inward from the knife edge; an upper die having an annular end face that overlies the upper sheet and registers with the die groove of the lower die; a punch button that is reciprocable within the upper die and registers with the opening in the lower die; a coil compression spring acting to urge the punch button to an extended position from the upper die in which the punch button extends into the opening in the lower die; and a ring-shaped grommet having a hollow interior receiving the punch button, an annular upper end flange for engagement by the annular end face of the upper die, and an axial extending wall of greater length than the stacked thickness of the upper and lower metal sheets, said axial extending wall having a metal piercing point at the terminal end thereof that registers with the knife edge of the lower die so that upon lowering of the upper die the annular end face forces the metal piercing point to pierce through the stacked upper and lower sheets and be deflected by the die groove of the lower die to bend the axial extending wall radially outward and upward to engage with the lower sheet whereby the sheets are attached together by capture between the annular upper end flange and the outward bent axial extending wall and the hollow ring shape of the grommet provides a reinforced aperture through the attached together sheets.
 15. The apparatus of claim 7 further comprising said spring-loaded punch having a dome shaped end face that engages the top sheet and bends the severed portions of the upper and lower sheets for disposal through the opening in the center of the lower die surface.
 16. The apparatus of claim 14 further comprising said opening of the lower die being a stepped bore having an upper portion that is of a diameter to receive the punch and a lower chute portion that is of a diameter greater than the diameter of the punch face to facilitate the disposal of the severed discs.
 17. The apparatus of claim 16 further comprising said spring-loaded punch having a dome shaped end face that engages the top sheet and bends the severed portions of the upper and lower sheets for disposal through the opening in the center of the lower die surface. 